.../platforms/pseries/hotplug-memory.c | 14 ++----- drivers/base/memory.c | 38 +++++++------------ drivers/base/node.c | 4 +- drivers/s390/char/sclp_mem.c | 17 ++++----- include/linux/memory.h | 7 +++- mm/memory_hotplug.c | 5 +-- 6 files changed, 35 insertions(+), 50 deletions(-)
Rename the memory block lookup helper to make the acquired reference
explicit, add memory_block_put() to wrap put_device(), and collapse the
redundant section-number wrapper into a single block-id based lookup
interface.
This makes it clearer to callers that a successful lookup holds a
reference that must be dropped, reducing the chance of forgetting the
matching put and leaking the memory block device reference.
Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
.../platforms/pseries/hotplug-memory.c | 14 ++-----
drivers/base/memory.c | 38 +++++++------------
drivers/base/node.c | 4 +-
drivers/s390/char/sclp_mem.c | 17 ++++-----
include/linux/memory.h | 7 +++-
mm/memory_hotplug.c | 5 +--
6 files changed, 35 insertions(+), 50 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 75f85a5da981..94f3b57054b6 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -164,13 +164,7 @@ static int update_lmb_associativity_index(struct drmem_lmb *lmb)
static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
{
- unsigned long section_nr;
- struct memory_block *mem_block;
-
- section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
-
- mem_block = find_memory_block(section_nr);
- return mem_block;
+ return memory_block_get(phys_to_block_id(lmb->base_addr));
}
static int get_lmb_range(u32 drc_index, int n_lmbs,
@@ -220,7 +214,7 @@ static int dlpar_change_lmb_state(struct drmem_lmb *lmb, bool online)
else
rc = 0;
- put_device(&mem_block->dev);
+ memory_block_put(mem_block);
return rc;
}
@@ -319,12 +313,12 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
rc = dlpar_offline_lmb(lmb);
if (rc) {
- put_device(&mem_block->dev);
+ memory_block_put(mem_block);
return rc;
}
__remove_memory(lmb->base_addr, memory_block_size);
- put_device(&mem_block->dev);
+ memory_block_put(mem_block);
/* Update memory regions for memory remove */
memblock_remove(lmb->base_addr, memory_block_size);
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 11d57cfa8d72..5b5d41089e81 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -649,7 +649,7 @@ int __weak arch_get_memory_phys_device(unsigned long start_pfn)
*
* Called under device_hotplug_lock.
*/
-struct memory_block *find_memory_block_by_id(unsigned long block_id)
+struct memory_block *memory_block_get(unsigned long block_id)
{
struct memory_block *mem;
@@ -659,16 +659,6 @@ struct memory_block *find_memory_block_by_id(unsigned long block_id)
return mem;
}
-/*
- * Called under device_hotplug_lock.
- */
-struct memory_block *find_memory_block(unsigned long section_nr)
-{
- unsigned long block_id = memory_block_id(section_nr);
-
- return find_memory_block_by_id(block_id);
-}
-
static struct attribute *memory_memblk_attrs[] = {
&dev_attr_phys_index.attr,
&dev_attr_state.attr,
@@ -701,7 +691,7 @@ static int __add_memory_block(struct memory_block *memory)
ret = device_register(&memory->dev);
if (ret) {
- put_device(&memory->dev);
+ memory_block_put(memory);
return ret;
}
ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
@@ -795,9 +785,9 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
struct memory_block *mem;
int ret = 0;
- mem = find_memory_block_by_id(block_id);
+ mem = memory_block_get(block_id);
if (mem) {
- put_device(&mem->dev);
+ memory_block_put(mem);
return -EEXIST;
}
mem = kzalloc_obj(*mem);
@@ -845,8 +835,8 @@ static void remove_memory_block(struct memory_block *memory)
memory->group = NULL;
}
- /* drop the ref. we got via find_memory_block() */
- put_device(&memory->dev);
+ /* drop the ref. we got via memory_block_get() */
+ memory_block_put(memory);
device_unregister(&memory->dev);
}
@@ -880,7 +870,7 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
end_block_id = block_id;
for (block_id = start_block_id; block_id != end_block_id;
block_id++) {
- mem = find_memory_block_by_id(block_id);
+ mem = memory_block_get(block_id);
if (WARN_ON_ONCE(!mem))
continue;
remove_memory_block(mem);
@@ -908,7 +898,7 @@ void remove_memory_block_devices(unsigned long start, unsigned long size)
return;
for (block_id = start_block_id; block_id != end_block_id; block_id++) {
- mem = find_memory_block_by_id(block_id);
+ mem = memory_block_get(block_id);
if (WARN_ON_ONCE(!mem))
continue;
num_poisoned_pages_sub(-1UL, memblk_nr_poison(mem));
@@ -1015,12 +1005,12 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
return 0;
for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
- mem = find_memory_block_by_id(block_id);
+ mem = memory_block_get(block_id);
if (!mem)
continue;
ret = func(mem, arg);
- put_device(&mem->dev);
+ memory_block_put(mem);
if (ret)
break;
}
@@ -1228,22 +1218,22 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
void memblk_nr_poison_inc(unsigned long pfn)
{
const unsigned long block_id = pfn_to_block_id(pfn);
- struct memory_block *mem = find_memory_block_by_id(block_id);
+ struct memory_block *mem = memory_block_get(block_id);
if (mem) {
atomic_long_inc(&mem->nr_hwpoison);
- put_device(&mem->dev);
+ memory_block_put(mem);
}
}
void memblk_nr_poison_sub(unsigned long pfn, long i)
{
const unsigned long block_id = pfn_to_block_id(pfn);
- struct memory_block *mem = find_memory_block_by_id(block_id);
+ struct memory_block *mem = memory_block_get(block_id);
if (mem) {
atomic_long_sub(i, &mem->nr_hwpoison);
- put_device(&mem->dev);
+ memory_block_put(mem);
}
}
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 126f66aa2c3e..b3333ca92090 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -847,13 +847,13 @@ static void register_memory_blocks_under_nodes(void)
for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
struct memory_block *mem;
- mem = find_memory_block_by_id(block_id);
+ mem = memory_block_get(block_id);
if (!mem)
continue;
memory_block_add_nid_early(mem, nid);
do_register_memory_block_under_node(nid, mem);
- put_device(&mem->dev);
+ memory_block_put(mem);
}
}
diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
index 78c054e26d17..6df1926d4c62 100644
--- a/drivers/s390/char/sclp_mem.c
+++ b/drivers/s390/char/sclp_mem.c
@@ -204,7 +204,7 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
addr = sclp_mem->id * block_size;
/*
* Hold device_hotplug_lock when adding/removing memory blocks.
- * Additionally, also protect calls to find_memory_block() and
+ * Additionally, also protect calls to memory_block_get() and
* sclp_attach_storage().
*/
rc = lock_device_hotplug_sysfs();
@@ -231,20 +231,19 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
sclp_mem_change_state(addr, block_size, 0);
goto out_unlock;
}
- mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
- put_device(&mem->dev);
+ mem = memory_block_get(phys_to_block_id(addr));
+ memory_block_put(mem);
WRITE_ONCE(sclp_mem->config, 1);
} else {
if (!sclp_mem->config)
goto out_unlock;
- mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
+ mem = memory_block_get(phys_to_block_id(addr));
if (mem->state != MEM_OFFLINE) {
- put_device(&mem->dev);
+ memory_block_put(mem);
rc = -EBUSY;
goto out_unlock;
}
- /* drop the ref just got via find_memory_block() */
- put_device(&mem->dev);
+ memory_block_put(mem);
sclp_mem_change_state(addr, block_size, 0);
__remove_memory(addr, block_size);
#ifdef CONFIG_KASAN
@@ -294,11 +293,11 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att
return rc;
block_size = memory_block_size_bytes();
sclp_mem = container_of(kobj, struct sclp_mem, kobj);
- mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(sclp_mem->id * block_size)));
+ mem = memory_block_get(phys_to_block_id(sclp_mem->id * block_size));
if (!mem) {
WRITE_ONCE(sclp_mem->memmap_on_memory, value);
} else {
- put_device(&mem->dev);
+ memory_block_put(mem);
rc = -EBUSY;
}
unlock_device_hotplug();
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 5bb5599c6b2b..29edef1f975c 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
void remove_memory_block_devices(unsigned long start, unsigned long size);
extern void memory_dev_init(void);
extern int memory_notify(enum memory_block_state state, void *v);
-extern struct memory_block *find_memory_block(unsigned long section_nr);
+extern struct memory_block *memory_block_get(unsigned long block_id);
+static inline void memory_block_put(struct memory_block *mem)
+{
+ put_device(&mem->dev);
+}
typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
extern int walk_memory_blocks(unsigned long start, unsigned long size,
void *arg, walk_memory_blocks_func_t func);
@@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
struct memory_group *excluded, void *arg);
-struct memory_block *find_memory_block_by_id(unsigned long block_id);
#define hotplug_memory_notifier(fn, pri) ({ \
static __meminitdata struct notifier_block fn##_mem_nb =\
{ .notifier_call = fn, .priority = pri };\
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 462d8dcd636d..890c6453e887 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
struct vmem_altmap *altmap = NULL;
struct memory_block *mem;
- mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
+ mem = memory_block_get(phys_to_block_id(cur_start));
if (WARN_ON_ONCE(!mem))
continue;
altmap = mem->altmap;
mem->altmap = NULL;
- /* drop the ref. we got via find_memory_block() */
- put_device(&mem->dev);
+ memory_block_put(mem);
remove_memory_block_devices(cur_start, memblock_size);
base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
--
2.54.0On 5/11/26 4:48 PM, Muchun Song wrote:
> Rename the memory block lookup helper to make the acquired reference
> explicit, add memory_block_put() to wrap put_device(), and collapse the
> redundant section-number wrapper into a single block-id based lookup
> interface.
>
> This makes it clearer to callers that a successful lookup holds a
> reference that must be dropped, reducing the chance of forgetting the
> matching put and leaking the memory block device reference.
>
> Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> .../platforms/pseries/hotplug-memory.c | 14 ++-----
> drivers/base/memory.c | 38 +++++++------------
> drivers/base/node.c | 4 +-
> drivers/s390/char/sclp_mem.c | 17 ++++-----
> include/linux/memory.h | 7 +++-
> mm/memory_hotplug.c | 5 +--
> 6 files changed, 35 insertions(+), 50 deletions(-)
Hi
I did some basic DLPAR memory add/remove tests on PowerPC with this
patch, and it is working fine.
Initial memory
==============
[]# cat /proc/meminfo |grep -i MemTotal
MemTotal: 205169920 kB
After Add
=========
[]# cat /proc/meminfo |grep -i MemTotal
MemTotal: 247112960 kB
After Remove
============
[]# cat /proc/meminfo |grep -i MemTotal
MemTotal: 173729024 kB
[]#
Tested-by: Donet Tom <donettom@linux.ibm.com>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 75f85a5da981..94f3b57054b6 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -164,13 +164,7 @@ static int update_lmb_associativity_index(struct drmem_lmb *lmb)
>
> static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
> {
> - unsigned long section_nr;
> - struct memory_block *mem_block;
> -
> - section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
> -
> - mem_block = find_memory_block(section_nr);
> - return mem_block;
> + return memory_block_get(phys_to_block_id(lmb->base_addr));
> }
>
> static int get_lmb_range(u32 drc_index, int n_lmbs,
> @@ -220,7 +214,7 @@ static int dlpar_change_lmb_state(struct drmem_lmb *lmb, bool online)
> else
> rc = 0;
>
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> return rc;
> }
> @@ -319,12 +313,12 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
>
> rc = dlpar_offline_lmb(lmb);
> if (rc) {
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
> return rc;
> }
>
> __remove_memory(lmb->base_addr, memory_block_size);
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> /* Update memory regions for memory remove */
> memblock_remove(lmb->base_addr, memory_block_size);
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 11d57cfa8d72..5b5d41089e81 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -649,7 +649,7 @@ int __weak arch_get_memory_phys_device(unsigned long start_pfn)
> *
> * Called under device_hotplug_lock.
> */
> -struct memory_block *find_memory_block_by_id(unsigned long block_id)
> +struct memory_block *memory_block_get(unsigned long block_id)
> {
> struct memory_block *mem;
>
> @@ -659,16 +659,6 @@ struct memory_block *find_memory_block_by_id(unsigned long block_id)
> return mem;
> }
>
> -/*
> - * Called under device_hotplug_lock.
> - */
> -struct memory_block *find_memory_block(unsigned long section_nr)
> -{
> - unsigned long block_id = memory_block_id(section_nr);
> -
> - return find_memory_block_by_id(block_id);
> -}
> -
> static struct attribute *memory_memblk_attrs[] = {
> &dev_attr_phys_index.attr,
> &dev_attr_state.attr,
> @@ -701,7 +691,7 @@ static int __add_memory_block(struct memory_block *memory)
>
> ret = device_register(&memory->dev);
> if (ret) {
> - put_device(&memory->dev);
> + memory_block_put(memory);
> return ret;
> }
> ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> @@ -795,9 +785,9 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
> struct memory_block *mem;
> int ret = 0;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (mem) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> return -EEXIST;
> }
> mem = kzalloc_obj(*mem);
> @@ -845,8 +835,8 @@ static void remove_memory_block(struct memory_block *memory)
> memory->group = NULL;
> }
>
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&memory->dev);
> + /* drop the ref. we got via memory_block_get() */
> + memory_block_put(memory);
> device_unregister(&memory->dev);
> }
>
> @@ -880,7 +870,7 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> end_block_id = block_id;
> for (block_id = start_block_id; block_id != end_block_id;
> block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> remove_memory_block(mem);
> @@ -908,7 +898,7 @@ void remove_memory_block_devices(unsigned long start, unsigned long size)
> return;
>
> for (block_id = start_block_id; block_id != end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> num_poisoned_pages_sub(-1UL, memblk_nr_poison(mem));
> @@ -1015,12 +1005,12 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
> return 0;
>
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> ret = func(mem, arg);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> if (ret)
> break;
> }
> @@ -1228,22 +1218,22 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> void memblk_nr_poison_inc(unsigned long pfn)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_inc(&mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> void memblk_nr_poison_sub(unsigned long pfn, long i)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_sub(i, &mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 126f66aa2c3e..b3333ca92090 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -847,13 +847,13 @@ static void register_memory_blocks_under_nodes(void)
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> struct memory_block *mem;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> memory_block_add_nid_early(mem, nid);
> do_register_memory_block_under_node(nid, mem);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
>
> }
> diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
> index 78c054e26d17..6df1926d4c62 100644
> --- a/drivers/s390/char/sclp_mem.c
> +++ b/drivers/s390/char/sclp_mem.c
> @@ -204,7 +204,7 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> addr = sclp_mem->id * block_size;
> /*
> * Hold device_hotplug_lock when adding/removing memory blocks.
> - * Additionally, also protect calls to find_memory_block() and
> + * Additionally, also protect calls to memory_block_get() and
> * sclp_attach_storage().
> */
> rc = lock_device_hotplug_sysfs();
> @@ -231,20 +231,19 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> sclp_mem_change_state(addr, block_size, 0);
> goto out_unlock;
> }
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> - put_device(&mem->dev);
> + mem = memory_block_get(phys_to_block_id(addr));
> + memory_block_put(mem);
> WRITE_ONCE(sclp_mem->config, 1);
> } else {
> if (!sclp_mem->config)
> goto out_unlock;
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> + mem = memory_block_get(phys_to_block_id(addr));
> if (mem->state != MEM_OFFLINE) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> goto out_unlock;
> }
> - /* drop the ref just got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
> sclp_mem_change_state(addr, block_size, 0);
> __remove_memory(addr, block_size);
> #ifdef CONFIG_KASAN
> @@ -294,11 +293,11 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att
> return rc;
> block_size = memory_block_size_bytes();
> sclp_mem = container_of(kobj, struct sclp_mem, kobj);
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(sclp_mem->id * block_size)));
> + mem = memory_block_get(phys_to_block_id(sclp_mem->id * block_size));
> if (!mem) {
> WRITE_ONCE(sclp_mem->memmap_on_memory, value);
> } else {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> }
> unlock_device_hotplug();
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 5bb5599c6b2b..29edef1f975c 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> void remove_memory_block_devices(unsigned long start, unsigned long size);
> extern void memory_dev_init(void);
> extern int memory_notify(enum memory_block_state state, void *v);
> -extern struct memory_block *find_memory_block(unsigned long section_nr);
> +extern struct memory_block *memory_block_get(unsigned long block_id);
> +static inline void memory_block_put(struct memory_block *mem)
> +{
> + put_device(&mem->dev);
> +}
> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
> extern int walk_memory_blocks(unsigned long start, unsigned long size,
> void *arg, walk_memory_blocks_func_t func);
> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> struct memory_group *excluded, void *arg);
> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
> #define hotplug_memory_notifier(fn, pri) ({ \
> static __meminitdata struct notifier_block fn##_mem_nb =\
> { .notifier_call = fn, .priority = pri };\
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 462d8dcd636d..890c6453e887 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
> struct vmem_altmap *altmap = NULL;
> struct memory_block *mem;
>
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
> + mem = memory_block_get(phys_to_block_id(cur_start));
> if (WARN_ON_ONCE(!mem))
> continue;
>
> altmap = mem->altmap;
> mem->altmap = NULL;
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
>
> remove_memory_block_devices(cur_start, memblock_size);
>
>
> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
> On May 12, 2026, at 14:52, Donet Tom <donettom@linux.ibm.com> wrote: > > On 5/11/26 4:48 PM, Muchun Song wrote: > >> Rename the memory block lookup helper to make the acquired reference >> explicit, add memory_block_put() to wrap put_device(), and collapse the >> redundant section-number wrapper into a single block-id based lookup >> interface. >> >> This makes it clearer to callers that a successful lookup holds a >> reference that must be dropped, reducing the chance of forgetting the >> matching put and leaking the memory block device reference. >> >> Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t >> Signed-off-by: Muchun Song <songmuchun@bytedance.com> >> --- >> .../platforms/pseries/hotplug-memory.c | 14 ++----- >> drivers/base/memory.c | 38 +++++++------------ >> drivers/base/node.c | 4 +- >> drivers/s390/char/sclp_mem.c | 17 ++++----- >> include/linux/memory.h | 7 +++- >> mm/memory_hotplug.c | 5 +-- >> 6 files changed, 35 insertions(+), 50 deletions(-) > > > > Hi > > I did some basic DLPAR memory add/remove tests on PowerPC with this patch, and it is working fine. > > Initial memory > ============== > []# cat /proc/meminfo |grep -i MemTotal > MemTotal: 205169920 kB > > After Add > ========= > []# cat /proc/meminfo |grep -i MemTotal > MemTotal: 247112960 kB > > After Remove > ============ > []# cat /proc/meminfo |grep -i MemTotal > MemTotal: 173729024 kB > []# > > Tested-by: Donet Tom <donettom@linux.ibm.com> Really thanks for your testing. Thanks, Muchun.
On Mon, May 11, 2026 at 07:18:00PM +0800, Muchun Song wrote:
> Rename the memory block lookup helper to make the acquired reference
> explicit, add memory_block_put() to wrap put_device(), and collapse the
> redundant section-number wrapper into a single block-id based lookup
> interface.
>
> This makes it clearer to callers that a successful lookup holds a
> reference that must be dropped, reducing the chance of forgetting the
> matching put and leaking the memory block device reference.
As David said, let's reference more of what you've done in the various
refactorings.
>
> Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
LGTM overall, so:
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
> ---
> .../platforms/pseries/hotplug-memory.c | 14 ++-----
> drivers/base/memory.c | 38 +++++++------------
> drivers/base/node.c | 4 +-
> drivers/s390/char/sclp_mem.c | 17 ++++-----
> include/linux/memory.h | 7 +++-
> mm/memory_hotplug.c | 5 +--
> 6 files changed, 35 insertions(+), 50 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 75f85a5da981..94f3b57054b6 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -164,13 +164,7 @@ static int update_lmb_associativity_index(struct drmem_lmb *lmb)
>
> static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
> {
> - unsigned long section_nr;
> - struct memory_block *mem_block;
> -
> - section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
> -
> - mem_block = find_memory_block(section_nr);
> - return mem_block;
> + return memory_block_get(phys_to_block_id(lmb->base_addr));
Ah nice I see this does the equivalent via phys_to_block_id() and
pfn_to_block_id() so that's a nice cleanup.
> }
>
> static int get_lmb_range(u32 drc_index, int n_lmbs,
> @@ -220,7 +214,7 @@ static int dlpar_change_lmb_state(struct drmem_lmb *lmb, bool online)
> else
> rc = 0;
>
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> return rc;
> }
> @@ -319,12 +313,12 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
>
> rc = dlpar_offline_lmb(lmb);
> if (rc) {
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
> return rc;
> }
>
> __remove_memory(lmb->base_addr, memory_block_size);
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> /* Update memory regions for memory remove */
> memblock_remove(lmb->base_addr, memory_block_size);
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 11d57cfa8d72..5b5d41089e81 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -649,7 +649,7 @@ int __weak arch_get_memory_phys_device(unsigned long start_pfn)
> *
> * Called under device_hotplug_lock.
> */
> -struct memory_block *find_memory_block_by_id(unsigned long block_id)
> +struct memory_block *memory_block_get(unsigned long block_id)
> {
> struct memory_block *mem;
>
> @@ -659,16 +659,6 @@ struct memory_block *find_memory_block_by_id(unsigned long block_id)
> return mem;
> }
>
> -/*
> - * Called under device_hotplug_lock.
> - */
> -struct memory_block *find_memory_block(unsigned long section_nr)
> -{
> - unsigned long block_id = memory_block_id(section_nr);
> -
> - return find_memory_block_by_id(block_id);
> -}
> -
> static struct attribute *memory_memblk_attrs[] = {
> &dev_attr_phys_index.attr,
> &dev_attr_state.attr,
> @@ -701,7 +691,7 @@ static int __add_memory_block(struct memory_block *memory)
>
> ret = device_register(&memory->dev);
> if (ret) {
> - put_device(&memory->dev);
> + memory_block_put(memory);
> return ret;
> }
> ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> @@ -795,9 +785,9 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
> struct memory_block *mem;
> int ret = 0;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (mem) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> return -EEXIST;
> }
> mem = kzalloc_obj(*mem);
> @@ -845,8 +835,8 @@ static void remove_memory_block(struct memory_block *memory)
> memory->group = NULL;
> }
>
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&memory->dev);
> + /* drop the ref. we got via memory_block_get() */
> + memory_block_put(memory);
> device_unregister(&memory->dev);
> }
>
> @@ -880,7 +870,7 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> end_block_id = block_id;
> for (block_id = start_block_id; block_id != end_block_id;
> block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> remove_memory_block(mem);
> @@ -908,7 +898,7 @@ void remove_memory_block_devices(unsigned long start, unsigned long size)
> return;
>
> for (block_id = start_block_id; block_id != end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> num_poisoned_pages_sub(-1UL, memblk_nr_poison(mem));
> @@ -1015,12 +1005,12 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
> return 0;
>
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> ret = func(mem, arg);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> if (ret)
> break;
> }
> @@ -1228,22 +1218,22 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> void memblk_nr_poison_inc(unsigned long pfn)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_inc(&mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> void memblk_nr_poison_sub(unsigned long pfn, long i)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_sub(i, &mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 126f66aa2c3e..b3333ca92090 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -847,13 +847,13 @@ static void register_memory_blocks_under_nodes(void)
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> struct memory_block *mem;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> memory_block_add_nid_early(mem, nid);
> do_register_memory_block_under_node(nid, mem);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
>
> }
> diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
> index 78c054e26d17..6df1926d4c62 100644
> --- a/drivers/s390/char/sclp_mem.c
> +++ b/drivers/s390/char/sclp_mem.c
> @@ -204,7 +204,7 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> addr = sclp_mem->id * block_size;
> /*
> * Hold device_hotplug_lock when adding/removing memory blocks.
> - * Additionally, also protect calls to find_memory_block() and
> + * Additionally, also protect calls to memory_block_get() and
> * sclp_attach_storage().
> */
> rc = lock_device_hotplug_sysfs();
> @@ -231,20 +231,19 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> sclp_mem_change_state(addr, block_size, 0);
> goto out_unlock;
> }
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> - put_device(&mem->dev);
> + mem = memory_block_get(phys_to_block_id(addr));
> + memory_block_put(mem);
> WRITE_ONCE(sclp_mem->config, 1);
> } else {
> if (!sclp_mem->config)
> goto out_unlock;
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> + mem = memory_block_get(phys_to_block_id(addr));
> if (mem->state != MEM_OFFLINE) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> goto out_unlock;
> }
> - /* drop the ref just got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
> sclp_mem_change_state(addr, block_size, 0);
> __remove_memory(addr, block_size);
> #ifdef CONFIG_KASAN
> @@ -294,11 +293,11 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att
> return rc;
> block_size = memory_block_size_bytes();
> sclp_mem = container_of(kobj, struct sclp_mem, kobj);
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(sclp_mem->id * block_size)));
> + mem = memory_block_get(phys_to_block_id(sclp_mem->id * block_size));
> if (!mem) {
> WRITE_ONCE(sclp_mem->memmap_on_memory, value);
> } else {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> }
> unlock_device_hotplug();
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 5bb5599c6b2b..29edef1f975c 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> void remove_memory_block_devices(unsigned long start, unsigned long size);
> extern void memory_dev_init(void);
> extern int memory_notify(enum memory_block_state state, void *v);
> -extern struct memory_block *find_memory_block(unsigned long section_nr);
> +extern struct memory_block *memory_block_get(unsigned long block_id);
> +static inline void memory_block_put(struct memory_block *mem)
Yeah as David says, we remove extern's now as and when we touch that code :)
> +{
> + put_device(&mem->dev);
> +}
> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
> extern int walk_memory_blocks(unsigned long start, unsigned long size,
> void *arg, walk_memory_blocks_func_t func);
> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> struct memory_group *excluded, void *arg);
> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
> #define hotplug_memory_notifier(fn, pri) ({ \
> static __meminitdata struct notifier_block fn##_mem_nb =\
> { .notifier_call = fn, .priority = pri };\
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 462d8dcd636d..890c6453e887 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
> struct vmem_altmap *altmap = NULL;
> struct memory_block *mem;
>
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
> + mem = memory_block_get(phys_to_block_id(cur_start));
> if (WARN_ON_ONCE(!mem))
> continue;
>
> altmap = mem->altmap;
> mem->altmap = NULL;
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
>
> remove_memory_block_devices(cur_start, memblock_size);
>
>
> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
> --
> 2.54.0
>
On 5/11/26 13:18, Muchun Song wrote:
> Rename the memory block lookup helper to make the acquired reference
> explicit, add memory_block_put() to wrap put_device(), and collapse the
> redundant section-number wrapper into a single block-id based lookup
> interface.
>
> This makes it clearer to callers that a successful lookup holds a
> reference that must be dropped, reducing the chance of forgetting the
> matching put and leaking the memory block device reference.
Better mention some of the other changes here, like removing find_memory_block().
[...]
> unlock_device_hotplug();
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 5bb5599c6b2b..29edef1f975c 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> void remove_memory_block_devices(unsigned long start, unsigned long size);
> extern void memory_dev_init(void);
> extern int memory_notify(enum memory_block_state state, void *v);
> -extern struct memory_block *find_memory_block(unsigned long section_nr);
> +extern struct memory_block *memory_block_get(unsigned long block_id);
While at it, please drop the "extern".
> +static inline void memory_block_put(struct memory_block *mem)
> +{
> + put_device(&mem->dev);
> +}
> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
> extern int walk_memory_blocks(unsigned long start, unsigned long size,
> void *arg, walk_memory_blocks_func_t func);
> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> struct memory_group *excluded, void *arg);
> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
> #define hotplug_memory_notifier(fn, pri) ({ \
> static __meminitdata struct notifier_block fn##_mem_nb =\
> { .notifier_call = fn, .priority = pri };\
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 462d8dcd636d..890c6453e887 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
> struct vmem_altmap *altmap = NULL;
> struct memory_block *mem;
>
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
> + mem = memory_block_get(phys_to_block_id(cur_start));
> if (WARN_ON_ONCE(!mem))
> continue;
>
> altmap = mem->altmap;
> mem->altmap = NULL;
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
Would guards come in handy here?
In general
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
> On May 11, 2026, at 20:22, David Hildenbrand (Arm) <david@kernel.org> wrote:
>
> On 5/11/26 13:18, Muchun Song wrote:
>> Rename the memory block lookup helper to make the acquired reference
>> explicit, add memory_block_put() to wrap put_device(), and collapse the
>> redundant section-number wrapper into a single block-id based lookup
>> interface.
>>
>> This makes it clearer to callers that a successful lookup holds a
>> reference that must be dropped, reducing the chance of forgetting the
>> matching put and leaking the memory block device reference.
>
> Better mention some of the other changes here, like removing find_memory_block().
Will do.
>
> [...]
>
>> unlock_device_hotplug();
>> diff --git a/include/linux/memory.h b/include/linux/memory.h
>> index 5bb5599c6b2b..29edef1f975c 100644
>> --- a/include/linux/memory.h
>> +++ b/include/linux/memory.h
>> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
>> void remove_memory_block_devices(unsigned long start, unsigned long size);
>> extern void memory_dev_init(void);
>> extern int memory_notify(enum memory_block_state state, void *v);
>> -extern struct memory_block *find_memory_block(unsigned long section_nr);
>> +extern struct memory_block *memory_block_get(unsigned long block_id);
>
> While at it, please drop the "extern".
OK.
>
>> +static inline void memory_block_put(struct memory_block *mem)
>> +{
>> + put_device(&mem->dev);
>> +}
>> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
>> extern int walk_memory_blocks(unsigned long start, unsigned long size,
>> void *arg, walk_memory_blocks_func_t func);
>> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
>> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
>> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
>> struct memory_group *excluded, void *arg);
>> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
>> #define hotplug_memory_notifier(fn, pri) ({ \
>> static __meminitdata struct notifier_block fn##_mem_nb =\
>> { .notifier_call = fn, .priority = pri };\
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 462d8dcd636d..890c6453e887 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
>> struct vmem_altmap *altmap = NULL;
>> struct memory_block *mem;
>>
>> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
>> + mem = memory_block_get(phys_to_block_id(cur_start));
>> if (WARN_ON_ONCE(!mem))
>> continue;
>>
>> altmap = mem->altmap;
>> mem->altmap = NULL;
>> - /* drop the ref. we got via find_memory_block() */
>> - put_device(&mem->dev);
>> + memory_block_put(mem);
>
> Would guards come in handy here?
You mean to introduce something like:
scoped_guard(memory_block, id) {
}
Right? If yes, I will give it a try.
>
> In general
>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Thanks.
Muchun
>
> --
> Cheers,
>
> David
> On May 11, 2026, at 21:23, Muchun Song <muchun.song@linux.dev> wrote:
>
>
>
>> On May 11, 2026, at 20:22, David Hildenbrand (Arm) <david@kernel.org> wrote:
>>
>> On 5/11/26 13:18, Muchun Song wrote:
>>> Rename the memory block lookup helper to make the acquired reference
>>> explicit, add memory_block_put() to wrap put_device(), and collapse the
>>> redundant section-number wrapper into a single block-id based lookup
>>> interface.
>>>
>>> This makes it clearer to callers that a successful lookup holds a
>>> reference that must be dropped, reducing the chance of forgetting the
>>> matching put and leaking the memory block device reference.
>>
>> Better mention some of the other changes here, like removing find_memory_block().
>
> Will do.
>
>>
>> [...]
>>
>>> unlock_device_hotplug();
>>> diff --git a/include/linux/memory.h b/include/linux/memory.h
>>> index 5bb5599c6b2b..29edef1f975c 100644
>>> --- a/include/linux/memory.h
>>> +++ b/include/linux/memory.h
>>> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
>>> void remove_memory_block_devices(unsigned long start, unsigned long size);
>>> extern void memory_dev_init(void);
>>> extern int memory_notify(enum memory_block_state state, void *v);
>>> -extern struct memory_block *find_memory_block(unsigned long section_nr);
>>> +extern struct memory_block *memory_block_get(unsigned long block_id);
>>
>> While at it, please drop the "extern".
>
> OK.
>
>>
>>> +static inline void memory_block_put(struct memory_block *mem)
>>> +{
>>> + put_device(&mem->dev);
>>> +}
>>> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
>>> extern int walk_memory_blocks(unsigned long start, unsigned long size,
>>> void *arg, walk_memory_blocks_func_t func);
>>> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
>>> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
>>> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
>>> struct memory_group *excluded, void *arg);
>>> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
>>> #define hotplug_memory_notifier(fn, pri) ({ \
>>> static __meminitdata struct notifier_block fn##_mem_nb =\
>>> { .notifier_call = fn, .priority = pri };\
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 462d8dcd636d..890c6453e887 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
>>> struct vmem_altmap *altmap = NULL;
>>> struct memory_block *mem;
>>>
>>> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
>>> + mem = memory_block_get(phys_to_block_id(cur_start));
>>> if (WARN_ON_ONCE(!mem))
>>> continue;
>>>
>>> altmap = mem->altmap;
>>> mem->altmap = NULL;
>>> - /* drop the ref. we got via find_memory_block() */
>>> - put_device(&mem->dev);
>>> + memory_block_put(mem);
>>
>> Would guards come in handy here?
>
> You mean to introduce something like:
>
> scoped_guard(memory_block, id) {
> }
>
> Right? If yes, I will give it a try.
Hi David,
Did I get that right?
5 files changed, 26 insertions(+), 35 deletions(-)
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 5b5d41089e81..eba48320fc30 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -997,7 +997,6 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
{
const unsigned long start_block_id = phys_to_block_id(start);
const unsigned long end_block_id = phys_to_block_id(start + size - 1);
- struct memory_block *mem;
unsigned long block_id;
int ret = 0;
@@ -1005,12 +1004,11 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
return 0;
for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
- mem = memory_block_get(block_id);
+ CLASS(memory_block_get, mem)(block_id);
if (!mem)
continue;
ret = func(mem, arg);
- memory_block_put(mem);
if (ret)
break;
}
@@ -1218,23 +1216,19 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
void memblk_nr_poison_inc(unsigned long pfn)
{
const unsigned long block_id = pfn_to_block_id(pfn);
- struct memory_block *mem = memory_block_get(block_id);
+ CLASS(memory_block_get, mem)(block_id);
- if (mem) {
+ if (mem)
atomic_long_inc(&mem->nr_hwpoison);
- memory_block_put(mem);
- }
}
void memblk_nr_poison_sub(unsigned long pfn, long i)
{
const unsigned long block_id = pfn_to_block_id(pfn);
- struct memory_block *mem = memory_block_get(block_id);
+ CLASS(memory_block_get, mem)(block_id);
- if (mem) {
+ if (mem)
atomic_long_sub(i, &mem->nr_hwpoison);
- memory_block_put(mem);
- }
}
static unsigned long memblk_nr_poison(struct memory_block *mem)
diff --git a/drivers/base/node.c b/drivers/base/node.c
index b3333ca92090..32a5431cbb60 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -845,15 +845,12 @@ static void register_memory_blocks_under_nodes(void)
continue;
for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
- struct memory_block *mem;
-
- mem = memory_block_get(block_id);
+ CLASS(memory_block_get, mem)(block_id);
if (!mem)
continue;
memory_block_add_nid_early(mem, nid);
do_register_memory_block_under_node(nid, mem);
- memory_block_put(mem);
}
}
diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
index 6df1926d4c62..c9a1a7adcab6 100644
--- a/drivers/s390/char/sclp_mem.c
+++ b/drivers/s390/char/sclp_mem.c
@@ -237,13 +237,12 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
} else {
if (!sclp_mem->config)
goto out_unlock;
- mem = memory_block_get(phys_to_block_id(addr));
- if (mem->state != MEM_OFFLINE) {
- memory_block_put(mem);
- rc = -EBUSY;
- goto out_unlock;
+ scoped_class(memory_block_get, mem, phys_to_block_id(addr)) {
+ if (mem->state != MEM_OFFLINE) {
+ rc = -EBUSY;
+ goto out_unlock;
+ }
}
- memory_block_put(mem);
sclp_mem_change_state(addr, block_size, 0);
__remove_memory(addr, block_size);
#ifdef CONFIG_KASAN
@@ -293,12 +292,12 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att
return rc;
block_size = memory_block_size_bytes();
sclp_mem = container_of(kobj, struct sclp_mem, kobj);
- mem = memory_block_get(phys_to_block_id(sclp_mem->id * block_size));
- if (!mem) {
- WRITE_ONCE(sclp_mem->memmap_on_memory, value);
- } else {
- memory_block_put(mem);
- rc = -EBUSY;
+ scoped_class(memory_block_get, mem,
+ phys_to_block_id(sclp_mem->id * block_size)) {
+ if (!mem)
+ WRITE_ONCE(sclp_mem->memmap_on_memory, value);
+ else
+ rc = -EBUSY;
}
unlock_device_hotplug();
return rc ? rc : count;
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 463dc02f6cff..fb67041941a8 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -18,6 +18,7 @@
#include <linux/node.h>
#include <linux/compiler.h>
+#include <linux/cleanup.h>
#include <linux/mutex.h>
#include <linux/memory_hotplug.h>
@@ -163,6 +164,8 @@ static inline void memory_block_put(struct memory_block *mem)
{
put_device(&mem->dev);
}
+DEFINE_CLASS(memory_block_get, struct memory_block *, if (_T) memory_block_put(_T),
+ memory_block_get(block_id), unsigned long block_id)
typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
extern int walk_memory_blocks(unsigned long start, unsigned long size,
void *arg, walk_memory_blocks_func_t func);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 890c6453e887..3f89ffb286d6 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1415,15 +1415,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
for (cur_start = start; cur_start < start + size;
cur_start += memblock_size) {
struct vmem_altmap *altmap = NULL;
- struct memory_block *mem;
-
- mem = memory_block_get(phys_to_block_id(cur_start));
- if (WARN_ON_ONCE(!mem))
- continue;
+ scoped_class(memory_block_get, mem, phys_to_block_id(cur_start)) {
+ if (WARN_ON_ONCE(!mem))
+ continue;
- altmap = mem->altmap;
- mem->altmap = NULL;
- memory_block_put(mem);
+ altmap = mem->altmap;
+ mem->altmap = NULL;
+ }
remove_memory_block_devices(cur_start, memblock_size);
Thanks,
Muchun
>
>>
>> In general
>>
>> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
>
> Thanks.
>
> Muchun
>
>>
>> --
>> Cheers,
>>
>> David
On 5/12/26 05:11, Muchun Song wrote:
>
>
>> On May 11, 2026, at 21:23, Muchun Song <muchun.song@linux.dev> wrote:
>>
>>
>>
>>>
>>> On 5/11/26 13:18, Muchun Song wrote:
>>>
>>> Better mention some of the other changes here, like removing find_memory_block().
>>
>> Will do.
>>
>>>
>>> [...]
>>>
>>>
>>> While at it, please drop the "extern".
>>
>> OK.
>>
>>>
>>>
>>> Would guards come in handy here?
>>
>> You mean to introduce something like:
>>
>> scoped_guard(memory_block, id) {
>> }
>>
>> Right? If yes, I will give it a try.
>
> Hi David,
Hi,
>
> Did I get that right?
I assume so, but it's indeed rather ugly. ... in particular the CLASS and
scoped_class() thingies are pretty intuitive.
I thought we could use guard()/scoped_guard(), but reading the details, it's
mostly for locks only.
There is only one users of scoped_class in the tree (overlayfs).
Maybe, if we would do this properly, we would actually provide our own wrappers,
like
MEMORY_BLOCK
scoped_memory_block
not even providing "memory_block_get", as that would be implicit.
Like
MEMORY_BLOCK(mem)(block_id); // the second () is confusing
scoped_memory_block(mem, block_id) {
}
But that requires more thought, and I don't really know what the best practice
is there ...
So thanks for trying, but let's leave it as is for now.
--
Cheers,
David
On Mon, May 11, 2026 at 07:18:00PM +0800, Muchun Song wrote: > Rename the memory block lookup helper to make the acquired reference > explicit, add memory_block_put() to wrap put_device(), and collapse the > redundant section-number wrapper into a single block-id based lookup > interface. > > This makes it clearer to callers that a successful lookup holds a > reference that must be dropped, reducing the chance of forgetting the > matching put and leaking the memory block device reference. > > Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t > Signed-off-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Oscar Salvador <osalvador@suse.de> Thanks, it looks more solid to me! -- Oscar Salvador SUSE Labs
On Mon 11-05-26 19:18:00, Muchun Song wrote:
> Rename the memory block lookup helper to make the acquired reference
> explicit, add memory_block_put() to wrap put_device(), and collapse the
> redundant section-number wrapper into a single block-id based lookup
> interface.
>
> This makes it clearer to callers that a successful lookup holds a
> reference that must be dropped, reducing the chance of forgetting the
> matching put and leaking the memory block device reference.
>
> Link: https://lore.kernel.org/linux-mm/7887915D-E598-42B3-9AFE-BFFBACE8DE2D@linux.dev/#t
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
> ---
> .../platforms/pseries/hotplug-memory.c | 14 ++-----
> drivers/base/memory.c | 38 +++++++------------
> drivers/base/node.c | 4 +-
> drivers/s390/char/sclp_mem.c | 17 ++++-----
> include/linux/memory.h | 7 +++-
> mm/memory_hotplug.c | 5 +--
> 6 files changed, 35 insertions(+), 50 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 75f85a5da981..94f3b57054b6 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -164,13 +164,7 @@ static int update_lmb_associativity_index(struct drmem_lmb *lmb)
>
> static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
> {
> - unsigned long section_nr;
> - struct memory_block *mem_block;
> -
> - section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
> -
> - mem_block = find_memory_block(section_nr);
> - return mem_block;
> + return memory_block_get(phys_to_block_id(lmb->base_addr));
> }
>
> static int get_lmb_range(u32 drc_index, int n_lmbs,
> @@ -220,7 +214,7 @@ static int dlpar_change_lmb_state(struct drmem_lmb *lmb, bool online)
> else
> rc = 0;
>
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> return rc;
> }
> @@ -319,12 +313,12 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
>
> rc = dlpar_offline_lmb(lmb);
> if (rc) {
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
> return rc;
> }
>
> __remove_memory(lmb->base_addr, memory_block_size);
> - put_device(&mem_block->dev);
> + memory_block_put(mem_block);
>
> /* Update memory regions for memory remove */
> memblock_remove(lmb->base_addr, memory_block_size);
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 11d57cfa8d72..5b5d41089e81 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -649,7 +649,7 @@ int __weak arch_get_memory_phys_device(unsigned long start_pfn)
> *
> * Called under device_hotplug_lock.
> */
> -struct memory_block *find_memory_block_by_id(unsigned long block_id)
> +struct memory_block *memory_block_get(unsigned long block_id)
> {
> struct memory_block *mem;
>
> @@ -659,16 +659,6 @@ struct memory_block *find_memory_block_by_id(unsigned long block_id)
> return mem;
> }
>
> -/*
> - * Called under device_hotplug_lock.
> - */
> -struct memory_block *find_memory_block(unsigned long section_nr)
> -{
> - unsigned long block_id = memory_block_id(section_nr);
> -
> - return find_memory_block_by_id(block_id);
> -}
> -
> static struct attribute *memory_memblk_attrs[] = {
> &dev_attr_phys_index.attr,
> &dev_attr_state.attr,
> @@ -701,7 +691,7 @@ static int __add_memory_block(struct memory_block *memory)
>
> ret = device_register(&memory->dev);
> if (ret) {
> - put_device(&memory->dev);
> + memory_block_put(memory);
> return ret;
> }
> ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> @@ -795,9 +785,9 @@ static int add_memory_block(unsigned long block_id, int nid, unsigned long state
> struct memory_block *mem;
> int ret = 0;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (mem) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> return -EEXIST;
> }
> mem = kzalloc_obj(*mem);
> @@ -845,8 +835,8 @@ static void remove_memory_block(struct memory_block *memory)
> memory->group = NULL;
> }
>
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&memory->dev);
> + /* drop the ref. we got via memory_block_get() */
> + memory_block_put(memory);
> device_unregister(&memory->dev);
> }
>
> @@ -880,7 +870,7 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> end_block_id = block_id;
> for (block_id = start_block_id; block_id != end_block_id;
> block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> remove_memory_block(mem);
> @@ -908,7 +898,7 @@ void remove_memory_block_devices(unsigned long start, unsigned long size)
> return;
>
> for (block_id = start_block_id; block_id != end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (WARN_ON_ONCE(!mem))
> continue;
> num_poisoned_pages_sub(-1UL, memblk_nr_poison(mem));
> @@ -1015,12 +1005,12 @@ int walk_memory_blocks(unsigned long start, unsigned long size,
> return 0;
>
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> ret = func(mem, arg);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> if (ret)
> break;
> }
> @@ -1228,22 +1218,22 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> void memblk_nr_poison_inc(unsigned long pfn)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_inc(&mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> void memblk_nr_poison_sub(unsigned long pfn, long i)
> {
> const unsigned long block_id = pfn_to_block_id(pfn);
> - struct memory_block *mem = find_memory_block_by_id(block_id);
> + struct memory_block *mem = memory_block_get(block_id);
>
> if (mem) {
> atomic_long_sub(i, &mem->nr_hwpoison);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
> }
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 126f66aa2c3e..b3333ca92090 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -847,13 +847,13 @@ static void register_memory_blocks_under_nodes(void)
> for (block_id = start_block_id; block_id <= end_block_id; block_id++) {
> struct memory_block *mem;
>
> - mem = find_memory_block_by_id(block_id);
> + mem = memory_block_get(block_id);
> if (!mem)
> continue;
>
> memory_block_add_nid_early(mem, nid);
> do_register_memory_block_under_node(nid, mem);
> - put_device(&mem->dev);
> + memory_block_put(mem);
> }
>
> }
> diff --git a/drivers/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c
> index 78c054e26d17..6df1926d4c62 100644
> --- a/drivers/s390/char/sclp_mem.c
> +++ b/drivers/s390/char/sclp_mem.c
> @@ -204,7 +204,7 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> addr = sclp_mem->id * block_size;
> /*
> * Hold device_hotplug_lock when adding/removing memory blocks.
> - * Additionally, also protect calls to find_memory_block() and
> + * Additionally, also protect calls to memory_block_get() and
> * sclp_attach_storage().
> */
> rc = lock_device_hotplug_sysfs();
> @@ -231,20 +231,19 @@ static ssize_t sclp_config_mem_store(struct kobject *kobj, struct kobj_attribute
> sclp_mem_change_state(addr, block_size, 0);
> goto out_unlock;
> }
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> - put_device(&mem->dev);
> + mem = memory_block_get(phys_to_block_id(addr));
> + memory_block_put(mem);
> WRITE_ONCE(sclp_mem->config, 1);
> } else {
> if (!sclp_mem->config)
> goto out_unlock;
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(addr)));
> + mem = memory_block_get(phys_to_block_id(addr));
> if (mem->state != MEM_OFFLINE) {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> goto out_unlock;
> }
> - /* drop the ref just got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
> sclp_mem_change_state(addr, block_size, 0);
> __remove_memory(addr, block_size);
> #ifdef CONFIG_KASAN
> @@ -294,11 +293,11 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att
> return rc;
> block_size = memory_block_size_bytes();
> sclp_mem = container_of(kobj, struct sclp_mem, kobj);
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(sclp_mem->id * block_size)));
> + mem = memory_block_get(phys_to_block_id(sclp_mem->id * block_size));
> if (!mem) {
> WRITE_ONCE(sclp_mem->memmap_on_memory, value);
> } else {
> - put_device(&mem->dev);
> + memory_block_put(mem);
> rc = -EBUSY;
> }
> unlock_device_hotplug();
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 5bb5599c6b2b..29edef1f975c 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -158,7 +158,11 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
> void remove_memory_block_devices(unsigned long start, unsigned long size);
> extern void memory_dev_init(void);
> extern int memory_notify(enum memory_block_state state, void *v);
> -extern struct memory_block *find_memory_block(unsigned long section_nr);
> +extern struct memory_block *memory_block_get(unsigned long block_id);
> +static inline void memory_block_put(struct memory_block *mem)
> +{
> + put_device(&mem->dev);
> +}
> typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
> extern int walk_memory_blocks(unsigned long start, unsigned long size,
> void *arg, walk_memory_blocks_func_t func);
> @@ -171,7 +175,6 @@ struct memory_group *memory_group_find_by_id(int mgid);
> typedef int (*walk_memory_groups_func_t)(struct memory_group *, void *);
> int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func,
> struct memory_group *excluded, void *arg);
> -struct memory_block *find_memory_block_by_id(unsigned long block_id);
> #define hotplug_memory_notifier(fn, pri) ({ \
> static __meminitdata struct notifier_block fn##_mem_nb =\
> { .notifier_call = fn, .priority = pri };\
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 462d8dcd636d..890c6453e887 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1417,14 +1417,13 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
> struct vmem_altmap *altmap = NULL;
> struct memory_block *mem;
>
> - mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
> + mem = memory_block_get(phys_to_block_id(cur_start));
> if (WARN_ON_ONCE(!mem))
> continue;
>
> altmap = mem->altmap;
> mem->altmap = NULL;
> - /* drop the ref. we got via find_memory_block() */
> - put_device(&mem->dev);
> + memory_block_put(mem);
>
> remove_memory_block_devices(cur_start, memblock_size);
>
>
> base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83
> --
> 2.54.0
--
Michal Hocko
SUSE Labs
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